Field of the Invention
The present invention relates to a film forming apparatus for growing a film on a substrate.
Background Art
In plasma enhanced atomic layer deposition (PE-ALD) or atomic layer deposition (ALD) for example, a gas passed through a shower head is supplied to a substrate on a susceptor. US2005/0229848A1 discloses a film forming apparatus having a shower head in which two independent flow passages are formed.
A shower head in which a first passage and a second passage are formed is used as described below. First, a first gas supplied via the first passage is provided to a substrate. After the provision of the first gas, only purge gas is caused to flow through the first passage, thereby purging the first passage. Next, a second gas supplied via the second passage is provided to the substrate. After the provision of the second gas, only purge gas is caused to flow through the second passage, thereby purging the second passage. This sequence of operations is repeated to alternately supply the first gas and the second gas to the substrate.
If the second gas remains in the second passage when the first gas is supplied to the substrate, or if the first gas remains in the first passage when the second gas is supplied to the substrate, degradation in film forming quality occurs. It has been necessary to increase the purge time for avoidance of degradation in film forming quality. It is preferable to form first and second passages capable of being rapidly purged in order to avoid this drawback.